Titanium tetrafluoride as catalyst in production of polyesters



United States Patent TITANIUM TETRAFLUORIDE AS CATALYST IN PRODUCTION OF POLYESTERS John K. Sullivan, Akron, Ohio, assignor to The Goodyear Tire & Rubber Company, Akron, Ohio, a corporation of Ohio No Drawing. Application March 18, 1954,

Serial No. 417,218

16 Claims. (Cl. 26075) This, invention relates to the. preparation of polymeric glycol esters of terephthalic and isophthalic acids. More particularly this invention relates to an improvement in the method of preparing such superpolyesters by the alcoholysis of esters of these phthalic acids with a glycol and the subsequent polymerization of these glycol phthalates to high polymeric linear polyesters.

In the preparation of linear superpolyesters, one of the most satisfactory methods from the standpoint of simplicity of reaction and economy of operation has been the ester interchange method in which the esters of the acids are reacted with a glycol to form the diglycol ester of the acid or a low molecular weight polymeric polyester which is then polymerized to a high molecular weight polymeric polyester by a condensation reaction with splitting out of the glycol. This process, however, has not been entirely satisfactory because the initial ester interchange reaction is slow and because many of the materials that catalyze this reaction are not effective as catalysts for the subsequent condensation reaction.

Heretoiore various materials have been proposed as catalysts for the ester interchange reaction between the esters of dicarboxylic acids and glycols and for the subsequent polymerization or condensation reaction. Metals in the form of powder, chips, ribbon or wire have been suggested, as have surface catalysts such as broken glass or silica gel. The more successful of the catalysts used in the past, however, have been the alkaline materials such as the alkali metal and alkaline earth metal alcoholates, the alkali metal carbonates, or other alkaline reacting salts, alkaline earth oxides, and litharge.

Many of these materials are efiective catalysts for the initial'siinple ester interchange, and some of them catalyze the condensation reaction. However, many of the substances that catalyze the condensation reaction carry the polymerization only to a low degree or they do not promote the reaction efiectively enough to give reaction rates acceptable for a commercial process.

According to the present invention, it has been found that titanium tetrafiuoride catalyzes the ester interchange between glycols and terephthalate esters or isophthalate esters or mixtures of these esters and greatly accelerates the subsequent polymerization of the product. Moreover, the titanium tetrafluoride not only catalyzes the initial ester interchange reaction but also accelerates the rate of polymerization and permits the formation in relatively short reaction times of polymers of high molecular weight which may be readily processed to form products having excellent properties.

therefore, the terephthalate or insophthalate ester or a mixture thereof can be reacted with a glycol and the resultant glycol ester condensed to form a polymer, both stages of the reaction being carried out in the presence of titanium tetrafluoride. However, the his glycol ester may be prepared by any other suitable method, such as by reacting the sodium or potassium salt of the acid with ethylene chlorohydrin, or by reacting the acid with a techniques.

l atentecl Jan. 3, 1955 ICC large excess of the glycol, or by glycolysis using some catalyst which is a catalyst for the ester interchange but which is not a catalyst for the polymerization reaction. The bis ester or a low molecular weight polymer thereof can then be polymerized according to the usual known techniques using titanium tetrafluoride as the catalyst.

The following example illustrates the invention and how it. may be carried out:

Example Eleven parts of ethylene glycol and 11.0 parts of a /25 dimethyl terephthalate/dimethyl isophthalate mixture to which 0.0033 part (based on the total weight of dimethyl terephthala te and dimethyl isophthalate) of titanium tetrailuoride had been added were placed in a glass tube having inside diameter of 25 millimeters. The mixture of polyester-forming reactants was heated to 197 C. under nitrogen gas at. atmospheric pressure. A slow stream of nitrogen was passed through the mixture at the rate of approximately 100 bubbles per minute. Stirring was accomplished by mechanically rotating the nitrogen inlet tube which was fitted with three pairs of blades. The alcoholysis was carried substantially to completion as dermined by the recovery of approximately of the calculated amount of methanol. The time required for the alcoholysis reaction was five hours. At the conclusion of the alcoholysis the pressure was gradually reduced to Cut millimeter of mercury and the unreacted glycol distilled oii. By controlling the rate of flow of nitrogen into the evacuated system, the pressure was controlled and maintained at 1.0 millimeter of mercury. After 1.5 hours of condensation at 260 C. and 1 millimeter of mercury a 75/25 ethylene terephthalate/ethylene isophthalate copolymer having a melt viscosity at 280 C. of 11,230 poises was obtained. A similar run made under the same conditions using 0.03% litharge formed a 75/25 ethylene terephthalate/ethylene isophthalate copolymer having a viscosity of 3,838 poises.

While the practice of the invention has been illustrated with particular respect to the 75/ 25 ethylene terephthatare/ethylene isophthalate copolymer, ethylene terephthalate, ethylene isophthalate and copolymers containing any other ratio of ethylene terephthalate to ethylene isophthalate can similarly be made using titanium tetra iluoride as cataiyst for the ester interchange or polymerization reaction, by adjusting the proportions of the starti ng. materials.

In the practice of the invention, the preparation of the glycol ester and its subsequent polymerization is, in general, carried out in accordance with the usual, known Thus, the reaction is preferably carried out in the absence of oxygen, generally in an atmosphere of an inert gas such as nitrogen or the like, in order to lessen darkening and to make it possible to obtain a high molecular weight pale or colorless product. Bubbling the inert gas through the reacting mixture serves the added functions of agitation and of expediting the removal of volatile components formed by the reaction.

The amount of titanium tetrafiuoride used may be varied over wide concentrations. As is usual with catalysts, the amount will ordinarily be relatively small. As a general rule, the amount will be within the range of from 0.003 to 0.10 percent, based on the dialkyl phthalate. The preferred range is 0.003 to 0.05 percent, based on the dialkyl phthalate, to give a satisfactory reaction rate and a product of suitable viscosity and color.

The example given illustrates the invention particularly with respect to the dimethyl esters and ethylene glycol. The invention will also work eifectively with other esters of the phthalic acids such as the ethyl, propyl, butyl, and phenyl esters. Other glycols, such as the propylene glycols and the butylene glycols may also be used although ethylene glycol is preferred because of its low cost and ready availability.

While certain representative embodiments and details have been shown for the purpose of illustrating the invention, it will be apparent to those skilled in this art that various changes and modifications may be made therein without departing from the spirit or scope of the invention.

I claim:

1. In a process for preparing a polyester by the selfcondensation, with'the removal of glycol, of a his glycol ester of at least one acid selected from the group consisting of terephthalic acid and isophthalic acid, the improvement which comprises carrying out said condensation in the presence of a catalytic amount of titanium tetrafiuoride.

2. A process according to claim 1 in which the titanium tetrafluoride is used in amount of 0.003 to 0.05% by weight of the weight of the esters of terephthalic .acid and isophthalic acid.

3. In a process for preparing a polyester by subjecting at least one his ester of an acid selected from the group consisting of terephthalic and isophthalic acids to alcoholysis in the presence of an excess of a glycol and thereafter subjecting the bis glycol ester thus formed to self- -condensation, with the removal of the glycol, the improvement which comprises carrying out both the alcoholysis and condensation in the presence of a catalytic amount of titanium tetrafluoride.

7 4. A process according to claim 3 in which the titanium tetrafluoride is used in amount of 0.003 to 0.05% by weight of the weight of the esters of terephthalic acid and isophthalic acid. 5. In a process for preparing a polyester by the selfc'ondensation, with the removal of ethylene glycol, of a his ethylene glycol ester of at least one acid selected from the group consisting of terephthalic acid and isophthalic "acid, the improvement which comprises carrying out said condensation in the presence of a catalytic amount of titanium tetrafiuoride. 6. A process according to claim 5 in which the titanium tetrafluoride is used in amount of 0.003 to 0.05 by weight of the weight of the esters of terephthalic acid and isophthalic acid.

- 7. In a process for preparing a polyester by subjecting at least one his ester of an acid selected from the group consisting of terephthalic and isophthalic acids to alco- 'holy sisin the presence of an excess of ethylene glycol and thereafter subjecting the bis ethylene glycol ester thus formed to self-condensation, with the removal of ethylene glycol, the improvement which comprises carrying out both the alcoholysis and condensation in the presence of acatalytic amount of titanium tetrafluoride.

8. A process according to claim 7 in which the titanium tetrafluoride is used in amount of 0.003 to 0.05% by weight of the weight of the esters of terephthalic acid and isophthalic acid.

9. In a process for preparing a polyester by the selfcondensation, with the removal of ethylene glycol, of a his ethylene glycol ester of terephthalic acid, the improvement which comprises carrying out saidcondensation in the presence of a catalytic amount of titanium tetrafluoride.

10. In a process for preparing a polyester by the selfcondensation, with the removal of ethylene glycol, of a his ethylene glycol ester of isophthalic acid, the improvement which comprises carrying out said condensation in the presence of a catalytic amount of titanium tetrafiuoride.

11. In a process for preparing a copolyester by the self-condensation, with the removal of ethylene glycol, of a mixture of bis ethylene glycol terephthalate and bis ethylene glycol isophthalate, the improvement which comprises carrying out said condensation in the presence of a catalytic amount of titanium tetrafiuoride.

12. In a process for preparing a high molecular weight polyester by the self-condensation, with the removal of ethylene glycol, of a low molecular weight ethylene glycol polyester of at least one acid selected from the group consisting of terephthalic and isophthalic acid, the improvement which comprises carrying out said condensation in the presence of a catalytic amount of titanium tetrafluoride.

13. A process according to claim 9 in which the titanium tetratluoride is used in amount of 0.003 to 0.05% by weight of the Weight of his ethylene glycol ester of terephthalic acid.

-14. A process according to claim 10 in which the ti- 'tanium tetrafluoride is used in amount of 0.003 to 0.05 by weight of-the weight of bis ethylene glycol ester of isophthalic acid.

15. A process according to claim 11 in which the titanium tetrafluoride is used in amount of 0.003 to 0.05 by weight of the Weight of the mixture of his ethylene glycol terephthalate and his ethylene glycol isophthalate.

'16. A process according to claim 12 in which the titanium tetrafluoride is used in amount of 0.003 to 0.05 by weight of the weight of the low molecular weight ethylene glycol polyester.

References Cited in the file of this patent UNITED STATES PATENTS 2,428,455 Friedman Oct. 7, 1947 

1. IN A PROCESS FOR PREPARING A POLYESTER BY THE SELFCONDENSATION, WITH THE REMOVAL OF GLYCOL, OF A BIS GLYCOL ESTER OF AT LEAST ONE ACID SELECTED FROM THE GROUP CONSISTING OF TEREPHTHALIC ACID AND ISOPHTHALIC ACID, THE IMPROVEMENT WHICH COMPRISES CARRYING OUT SAID CONDENSATION IN THE PRESENCE OF A CATALYTIC AMOUNT OF TITANIUM TETRAFLUORIDE. 